Neil Munns/Pool/Reuters

LONDON — Britain is laughing at David Cameron.

The Prime Minister has got himself into an almighty pickle over the country’s relationship with the European Union and it’s entirely his own fault.

Ahead of a referendum on whether to leave the political and economic union, which is expected to be held on June 23, Cameron told voters he would fundamentally renegotiate the terms of the country’s deal with the EU—allowing Britain more power to curb immigration and exempting London from some of the pan-European rules on tax and welfare.

European leaders were never going to kowtow to Britain’s demands to unilaterally tear up the terms of a deal signed in 1973. But, after a humbling tour of European capitals—from Paris and Berlin to Riga, Bratislava and Reykjavik, Cameron returned to London claiming that he had won a great triumph.

Britain delivered its verdict on the so-called victory on Wednesday with the most hostile media reaction to a prime ministerial policy in recent history. “EU Stupid Boy” said The Sun, Britain’s best-selling newspaper. The Daily Mail described the deal as the “The Great Delusion,” while Metro said: “EU Are Joking.”

The concessions Cameron hopes to have officially sanctioned by the EU in the next month—which include time limits on welfare payments for immigrants—were denounced to his face in the House of Commons by members of all of Britain’s major political parties.

Jacob Rees-Mogg, a member of Cameron’s Conservative Party, said he had been unimpressed even by his leader’s original proposals, which were rejected by Europe. “The thin gruel has been further watered down. You have a fortnight, I think, in which to salvage your reputation as a negotiator,” Rees-Mogg told his boss.

The opposition parties—Labour, the Liberal Democrats and the Scottish National Party—all agree with Cameron that Britain should remain part of the European Union, but that didn’t stop them trash-talking his efforts to force his will on the rest of Europe.

Angus Robertson, the SNP’s leader in Westminster, said it was vital for Scottish and wider British interests that the country not be isolated from its European allies, but he said the prime minister has to stop “pretending” to have “won some major victory.”

Unlike Neville Chamberlain in 1938, Cameron hasn’t even had his scrap of paper signed as yet. Reactions to the draft proposal from France, Germany, and Poland suggest there will be even more watering down before the measures are approved.

That would leave Cameron looking even more foolish.

With Europe already rocked by a refugee crisis that threatens to destroy the border agreements that have brought continental European countries ever closer in the last 20 years, Britain’s exit from the union would be another major blow to its clout on the world stage.

Britain has always been internally conflicted over the EU, and has remained slightly detached—adrift in the Atlantic—in political as well as geographical terms.

Nonetheless, London’s close relationship with Washington and Britain’s relatively powerful economy and independent global influence have always been among the central strengths of the EU.

While British antipathy has been constant, there has been no serious attempt to leave the union since the 1970s.

That would have remained the case until David Cameron got nervous ahead of last year’s election. At a moment of weakness—when a rival right-wing party was surging in the polls—he promised a referendum on whether to leave the EU.

Right-wingers within his party, and voters attracted by the rhetoric of the UK Independence Party, deride Brussels’ influence on British laws, which include human-rights legislation and financial regulation and employment laws.

Immigration has also become an increasingly contentious issue. Free movement of people within the EU is one of the organization’s central philosophies. That became less popular as the EU expanded rapidly after 2004 to include 12 more countries, including Slovenia, Poland, and Bulgaria.

The current refugee crisis caused by instability and conflict in Syria, Libya, and Iraq has further heightened fears of an immigrant surge.

Cameron has failed to secure any leeway on immigration controls, but has proposed limiting the welfare payments that would be paid to immigrants in their first four years in the U.K.

The Institute for Public Policy Research said the proposal would not lead to a “substantial fall” in net migration. Phoebe Griffith, the associate director for migration, integration, said: “There’s very little evidence that EU migrants come to the UK to claim benefits.”

Cameron admits that there would be far more to do, even if his proposals are accepted by the EU, but there is little faith that Cameron would be able to get more in the future.

His Conservative colleague, Dr Sarah Wollaston, asked him in Parliament: “If this grudging and threadbare deal is the very best that the EU are prepared to concede to us, what serious hope is there of meaningful renegotiation once we are tied in?”